Hong Kong (CNN)China has imposed restrictions on the publication of academic research on the origins of the novel coronavirus, according to a central government directive and online notices published by two Chinese universities, that have since been removed from the web.Under the new policy, all academic papers on Covid-19 will be subject to extra vetting before being submitted for publication. Studies on the origin of the virus will receive extra scrutiny and must be approved by central government officials, according to the now-deleted posts.A medical expert in Hong Kong who collaborated with mainland researchers to publish a clinical analysis of Covid-19 cases in an international medical journal said his work did not undergo such vetting in February.The increased scrutiny appears to be the latest effort by the Chinese government to control the narrative on the origins of the coronavirus pandemic, which has claimed more than 100,000 lives and sickened 1.7 million people worldwide since it first broke out in the Chinese city of Wuhan in December. Since late January, Chinese researchers have published a series of Covid-19 studies in influential international medical journals. Some findings about early coronavirus cases — such as when human-to-human transition first appeared — have raised questions over the official government account of the outbreak and sparked controversy on Chinese social media. And now, Chinese authorities appear to be tightening their grip on the publication of Covid-19 research. A Chinese researcher who spoke on condition of anonymity due to fear of retaliation said the move was a worrying development that would likely obstruct important scientific research. “I think it is a coordinated effort from (the) Chinese government to control (the) narrative, and paint it as if the outbreak did not originate in China,” the researcher told CNN. “And I don’t think they will really tolerate any objective study to investigate the origination of this disease.” CNN has reached out to China’s Foreign Ministry for comment.